Question

Monosomy and trisomy can be represented as
A) \[2n + 1,{\text{ }}2n + 3\]
B) \[2n - 1,{\text{ }}2n - 2\]
C) \[2n,{\text{ }}2n + 1\]
D) \[2n - 1,{\text{ }}2n + 1\]

Answer 1

Hint: Chromosomal abnormalities are genetic illnesses caused by a change in one or more chromosomes, or by an aberrant chromosome layout. The following are the various forms of chromosomal abnormalities:
Aneuploidy is a situation in which chromosomes are lost or gained as a result of aberrant gene segregation during cell division.
Polyploidy is a condition in which the total number of chromosomes rises due to cytokinesis failure during cell division. Plants are the most common victims.
In humans, trisomy refers to the presence of an additional copy of a chromosome in one of the pairs, while monosomy refers to the absence of one of the chromosomes from the pair.

Complete answer:
Option A: Monosomy is a kind of aneuploidy in which a single chromosome from the normal complement is lost. \[2N - 1\] represents the chromosomal composition.
So option A is not correct.
Option B: The number of chromosomes in the cell where trisomy occurs is expressed as \[2n + 1\] if one chromosome is affected, \[2n + 1 + 1\] if two are affected, and so on.
So option B is not correct.
Option C: Monosomy is a kind of aneuploidy in which one homologous chromosome is missing \[\left( {2n - 1} \right)\]. Trisomy is defined as the presence of one chromosome in triplicate \[\left( {2n + 1} \right)\]. As a result, monosomy and trisomy can be written as \[2n - 1\] and \[2n + 1\], respectively. The presence of one chromosome in four copies is known as tetrasomy \[\left( {2n + 2} \right)\].
So option C is not correct.
Option D: Monosomy is a type of aneuploidy characterised by the absence of one homologous chromosome \[\left( {2n - 1} \right)\]. The presence of one chromosome in triplicate \[\left( {2n + 1} \right)\] is known as trisomy. Monosomy and trisomy can thus be expressed as \[2n - 1\] and \[2n + 1\], respectively. Tetrasomy \[\left( {2n + 2} \right)\] is defined as the presence of one chromosome in four copies. Disomy \[\left( {n + 1} \right)\] is the presence of one extra chromosome beyond the typical chromosome number in a haploid animal. Diploidy is defined as the presence of two copies of a full haploid set of chromosomes, denoted by the letters "\[2n\]".

Hence, option D is the correct answer.

Note:
Trisomy is a sort of polysomy disorder in which just one chromosome from each parent is present instead of the customary two. Monosomy refers to a diploid organism that is missing one chromosome from a single homologous pair.
Nullisomy is a term used to describe a diploid organism that has lost a pair of homologous chromosomes.
Tetrasomy is a disorder in which a single chromosome is duplicated four times in four homologous copies.